The present invention relates to the reaction of carbon monoxide with a C.sub.2 or higher aldehyde and water or an alcohol to produce an alpha-hydroxy carboxylic acid or an alpha-alkoxy carboxylic acid.
My related application Ser. No. 480,894, filed June 19, 1974, discloses a process for producing hydroxyacetic acid (commonly called glycolic acid) from carbon monoxide, formaldehyde, and water with a hydrogen fluoride catalyst.
My related application Ser. No. 532,563 entitled "Alkoxy Acid or Ester Preparation", filed on Dec. 13, 1974, discloses a process for producing alkoxy acetic acid from carbon monoxide, formaldehyde, alcohol, and water using a hydrogen fluoride catalyst.
U.S. Pat. No. 2,211,625 discloses the reaction of formaldehyde with carbon monoxide and an alcohol to produce an ester of glycolic acid in accordance with the following reaction: EQU HCHO + CO + ROH .fwdarw. HOCH.sub.2 COOR
according to this patent, a catalyst such as hydrochloric, sulfuric, or phosphoric acid can be used.
U.S. Pat. No. 2,211,624 discloses the reaction of formaldehyde, carbon monoxide, and an acid such as acetic acid to obtain an alpha-acyloxy acid in accordance with the following reaction: EQU HCHO + CO + CH.sub.3 COOH .fwdarw. CH.sub.3 COO--CH.sub.2 COOH
acid catalysts for the reaction according to this patent include hydrochloric, sulfuric, and phosphoric acid.
U.S. Pat. Nos. 2,152,852, 2,153,064, and 2,265,945 disclose hydroxy-acetic acid production from formaldehyde, carbon monoxide and water using acid catalysts. U.S. Pat. No. 2,265,945 discloses as follows at Col. 1, lines 22-40:
"The above and other objects of the invention are realized by dissolving an aldehyde, having more than 1 carbon atom, or one of its polymers, in water, or a suitable solvent medium, and preferably in the presence of a catalyst having acidic characteristics, subjecting the resulting solution to heat and pressure and an atmosphere of carbon monoxide, whereupon a hydroxy acid is obtained in accordance with the equation: RCHO+CO+HOH .fwdarw. RCH(OH)COOH in which R may be hydrogen, an alkyl, aryl, aralkyl, cyclic or alicyclic group. Thus, for example, acetaldehyde yields lactic acid and the higher aldehydes, correspondingly higher hydroxy acids. This reaction may be carried out by placing the mixture of aldehyde, water and catalyst in an autoclave, applying the necessary pressure by forcing in carbon monoxide and effecting the reaction by the application of heat."
According to all three of these patents -- that is, U.S. Pat. Nos. 2,152,852, 2,153,064 and 2,265,945 -- the acid catalysts disclosed are hydrochloric, sulfuric, phosphoric and inorganic acid salts such as potassium acid sulfate, sodium acid phosphate and boron fluoride. Temperatures disclosed for use in the processes of the patents are 50.degree. to 350.degree.C and more preferably 140.degree. to 225.degree.C. Pressures disclosed are 5 to 1500 atmospheres (75 to 23,000 psi) and higher. In the examples of all 3 of the patents, the only inorganic acid catalysts used are phosphoric acid, sulfuric acid and hydrochloric acid. The temperatures used in the examples of the patents are usually between 160.degree. and 200.degree.C, and the pressures usually about 900 atmospheres (13,500 psi) and essentially always above 300 atmospheres (4500 psi). The severe reaction conditions indicated for the carbonylation of formaldehyde such as the high reaction temperature in the presence of corrosive acids and very high CO pressure require expensive equipment made from corrosion-resistant materials. According to the disclosures in the patents, the reaction can be effected in a continuous manner by passing the formaldehyde or its equivalent, water or its equivalent, and acid catalyst through a reaction zone either cocurrently or countercurrently to the flow of carbon monoxide.